1. Field of the Invention
The present invention relates to a method for forming an inductor in a semiconductor device, and more specifically, to a method for forming an inductor in a semiconductor device wherein a thickness at the line and contact portions of the inductor being a passive device is made uniform and their height is easily controlled in RE MEMS, RFCMOS, Bipolor/SiGe and BiCMOS semiconductor devices, thus allowing a high Q inductor to be manufactured.
2. Discussion of Related Art
In RE MEMS, RFCMOS, Bipolor/SiGe and BiCMOS semiconductor devices, an inductor being a passive device is formed by means of a damascene process with the device higher integrated, and an inductor of a high quality is required.
FIG. 1A to FIG. 1F are cross-sectional views shown to explain a conventional method for forming an inductor in a semiconductor device.
Referring to FIG. 1A, a lower electrode 11 is formed using a conductive material such as copper on a substrate 10 in which a predetermined underlying structure constituting a semiconductor device is formed. A positive photoresist layer 12 is covered on the substrate 10 including the lower electrode 11.
By reference to FIG. 1B, a primary exposure process is performed for some of the positive photoresist layer 12 up to the lower electrode 11 using a first mask 13. A first exposure region 12H is thus formed in a portion in which a contact of an inductor will be formed.
Referring to FIG. 1C, a secondary exposure process is performed for a portion of the positive photoresist layer 12 in a predetermined thickness using a first mask 14. Second exposure regions 12T are thus formed in portions in which lines of the inductor will be formed.
By reference to FIG. 1D, the first and second exposure regions 12H and 12T are developed to form trenches 15 in which the lines of the inductor is to be formed and a via hole 16 in which a contact of the inductor is to be formed.
Referring to FIG. 1E, the trenches 15 and the via hole 16 are buried with copper, forming the inductor 17.
By reference to FIG. 1F, the positive photoresist layer 12 is stripped to form the inductor 17 that is spaced apart from the substrate 10 by a predetermined distance.
In recent years, as semiconductor devices are higher integrated and are multi-functioned, copper (Cu) has been widely used as a material of the inductor in order to implement the inductor of a high quality. In order to facilitate the use of copper, a damascene process is performed at the same time. In order to obtain a desired quality factor of the copper inductor, Cu lines of several μm in thickness are required. In the aforementioned conventional method, the depth of a photoresist layer developed is controlled depending on the time when light is illuminated by means of a positive photoresist layer, thus controlling the line thickness of an inductor that is completed. In this method, however, it is difficult to control the line thickness exactly and uniformly. This is because the amount of a photoresist developed is non-uniform due to various external environments such as the composition of the photoresist when the process is performed, the components or composition of a photoresist developer, a process condition, intensity and time of light illuminated and the like.